This invention relates generally to an ultrasonic transducer probe for use in transmitting and receiving ultrasonic energy to and from a body being scanned and more particularly to a probe suitable for use in an ultrasonic sector scanning system.
In recent years, ultrasonic scanning of regions of the human body have found wide applications. Among advantages of such scanning systems is that the energy required is low, thereby reducing the possibility of injury to a patient. There are no radiation side effects. The body is not invaded.
As is known, in such systems the ultrasound energy is transmitted in a beam of pulses each followed by a relatively long interval where no transmission occurs. During this interval the pulse energy is transmitted through the body. Whenever a pulse of energy strikes a boundary between two substances having different acoustic impedance, a portion of the ultrasound energy is reflected. Some of the reflected energy returns as an echo to the transmitting transducer. The beam produces additional echoes from deeper interfaces. The crystals which serve as transmitting transducers also serve as receiving transducers to convert the reflected ultrasound energy into electrical signals. These signals are amplified and displayed as static or dynamic patterns on a cathode ray tube. The relative position of the interfaces in the body are displayed.
A particular type of scanner used is a sector scanner. A sector scanner generally comprises an ultrasonic transducer (piezoelectric element) which is mounted to be driven. The drive moves the transducer, generally in the form of a flat circular object, back and forth in an arc scanning motion. During this process the transducer is pulsed with high voltage pulses at pulse repetition rates in the order of 3000 Hz. These pulses cause the piezoelectric element to mechanically ring thereby emitting high frequency sound waves in a beam. As the transducer scans, it forms a plurality of beams in a fan or sector shape. The beams impinge upon the structure within the body and when differences in acoustic impedance exist, energy is partially reflected back to the transducer element to cause the transducer to mechanically vibrate. At this point, the transducer element acts like a receiver and converts these mechanical vibrations to electrical energy. This energy is amplified and processed so that it can be displayed on a cathode ray tube.
The mechanical driving arrangement not only drives the transducer but also includes means for generating an electrical output representative of transducer position. The electrical output from the driving arrangement is processed and utilized to create horizontal and vertical signals to drive the vertical and horizontal deflection circuits of a cathode ray tube. The signals from the ultrasonic transducer are used to control the intensity of the cathode ray tube beam. The resultant image is a sector shaped representation of the internal organs of the body.
Another prior art system which allows real time examination of internal organs of the body such as the heart employs a catheter which has a rotating tip with a plurality of transducers. The transducers are selectively connected to a pulser to transmit ultrasonic sound into the body and to receive echoes therefrom. The echo pulses are processed and applied to a cathode ray tube whereby to provide sequential representations of the area at a rate which is dependent on the speed of rotation of the transducers and with a resolution which is dependent upon the pulse rate.
In copending application Ser. No. 807,438, entitled "Ultrasonic Transducer Probe" and assigned to the same assignee, there is described a rotary transducer probe including a head adapted to house drive means including bevel gears, commutating means including sliding contacts and position sensing means in the form of a light source and photodiode. Although the probe described in said copending application is satisfactory, the drive means introduces some jitter due to the engagement of the bevel gear teeth. The sliding contacts are subject to wear.